While jigsaw puzzles have been known and enjoyed by a wide segment of our society for a very long period time, innovations in this art appear to be few. The degree of complexity appears to be primarily increased by providing a background pattern having portions less distinctive from each other, an increased number of pieces, a smaller size of the pieces, and a closer similarity among the individual cuts without making too many of them interchangeable. The degree of difficulty for individual puzzles appears to be geared towards age groups and ability levels by changing the above variables.
Quite apart from puzzles, there are areas where people like to have their possessions individualized, for example the so-called "vanity plates" for automobiles, monogrammed shirts, and the like.
While the term jigsaw puzzle was no doubt partly derived from the name of a particular type of cutting machine, namely the jigsaw, modern jigsaw puzzles are made by many different machines other than the traditional jigsaw, for example by stamping out flat sheets of material much in the way cookies are cut out from a flat sheet of dough by a cookie cutter. Therefore, the term jigsaw puzzle is more descriptive of the type of puzzle than the machine used to make the puzzle. Generally, jigsaw puzzles are thought of as being made from a flat sheet of material whose thickness is generally immaterial, which is cut into a number of pieces as viewed in a plan view so that the pieces can be vertically assembled/disassembled but interlocked to prevent assembly/disassembly in any horizontal direction.